A denitration catalyst, a preparation method and application thereof

Abstract

The application provides a denitration catalyst and a preparation method and application thereof. The denitration catalyst comprises a carrier and a composite oxide active component loaded on the surface of the carrier; the carrier comprises a mesoporous SBA molecular sieve, and the chemical formula of the composite oxide active component is CeMO x wherein M is a doping element, and x is the number of O atoms required to satisfy valence balance; the particle size D90 of the composite oxide active component is 5-30 nm. The denitration catalyst prepared by the application has high surface acidity and redox capacity, CeMO x can enter the pore channel of the molecular sieve and interact with the elements in the molecular sieve framework, which effectively improves the sulfur dioxide poisoning resistance of the catalyst, so that the catalyst still has high catalytic activity and nitrogen selectivity in the use temperature range of 250-400 DEG C after sulfur dioxide poisoning.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification and environmental protection technology, specifically relating to a denitrification catalyst, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NO) x Nitrogen oxides (NOx) are one of the major air pollutants, and the combustion of fossil fuels is the primary source of NOx emissions. Excessive NOx levels in the atmosphere can cause a series of environmental and climatic problems, including acid rain, photochemical smog, and soil acidification. Traditional stationary source flue gas denitrification primarily uses ammonia selective catalytic reduction (NH3-SCR) technology, employing V2O5-WO3 / TiO2 or its modified forms as catalysts, with operating temperatures typically between 300 and 400°C. However, V2O5 in this catalyst is toxic, and its recovery and post-treatment have become bottlenecks restricting its development. Catalysts using cerium dioxide (CeO2) and modified cerium dioxide as active components have attracted widespread attention from researchers due to their excellent redox capabilities, fewer side reactions, and environmentally friendly characteristics.

[0003] Currently, boiler flue gas SCR denitrification catalysts face the problem of sulfur dioxide poisoning leading to catalyst deactivation in practical applications. This is because the coal ash produced during boiler combustion contains a certain amount of sulfur dioxide gas. This gas covers the catalyst surface and reacts with ammonia and cerium-based active components, forming ammonium sulfate that coats the catalyst surface, reducing the number of exposed active sites. Simultaneously, it leads to the formation of cerium sulfate, which is difficult to decompose, thereby damaging the catalyst's redox capacity and causing irreversible deactivation.

[0004] CN102416320A discloses a denitrification catalyst, relating to the field of catalyst technology. The catalyst comprises the following components in parts by weight: 75-85 parts titanium dioxide; 10-12 parts tungsten trioxide; 3-6 parts silicon dioxide; 2-3 parts vanadium pentoxide; 3-6 parts kapok pulp; 2-7 parts glass fiber; and 2-3 parts stearic acid. The components are mixed according to the specified parts by weight, stirred evenly, and then sequentially subjected to aging, pre-extrusion, secondary aging, extrusion molding, primary drying, secondary drying, high-temperature calcination, and finished product trimming before packaging to obtain the finished catalyst. CN107737588A discloses a denitrification catalyst whose raw materials, by weight, are 35-45 parts titanium dioxide, 2-5 parts antimony oxide, 10-20 parts glass fiber, 1-3 parts vanadium pentoxide, 3-6 parts molybdenum oxide, and 3-6 parts tungsten oxide.

[0005] However, the denitrification catalyst prepared by the above scheme is difficult to balance high-temperature and low-temperature catalytic activity, and the catalyst activity drops sharply after sulfur dioxide poisoning.

[0006] Therefore, improving the denitrification performance of denitrification catalysts in the presence of sulfur dioxide is crucial for saving flue gas purification costs in the coal-fired industry and improving waste gas treatment efficiency. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a denitrification catalyst, its preparation method, and its applications. The denitrification catalyst prepared by this invention exhibits high surface acidity and redox capability, with CeMO2 content... x It can enter the pores of the molecular sieve and interact with the elements in the molecular sieve framework, which effectively improves the catalyst's resistance to sulfur dioxide poisoning, thus ensuring that it still has high catalytic activity and nitrogen selectivity in the operating temperature range of 250-400℃ after sulfur dioxide poisoning.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a denitrification catalyst, characterized in that the denitrification catalyst comprises a support and a composite oxide active component supported on the surface of the support;

[0010] The support comprises a mesoporous SBA molecular sieve, and the chemical formula of the active component of the composite oxide is CeMO. x Where M is the doping element and x is the number of O atoms required to satisfy valence balance;

[0011] The particle size D90 of the active component of the composite oxide is 5-30 nm.

[0012] The denitration catalyst prepared in this invention has high surface acidity and redox ability, CeMO x It can enter the pores of the molecular sieve and interact with the elements in the molecular sieve framework, which effectively improves the catalyst's resistance to sulfur dioxide poisoning, thus ensuring that it still has high catalytic activity and nitrogen selectivity in the operating temperature range of 250 to 400°C after sulfur dioxide poisoning.

[0013] The CeMO of this invention x The doping element ratio of the active component and the particle size of the active component nanoparticles are easily adjustable. By changing the amount of surfactant added during synthesis, the size of the active component can be easily adjusted, thereby further improving the catalytic performance and sulfur dioxide resistance of the catalyst.

[0014] In this invention, CeMO xThe active components are fully dispersed on the molecular sieve support, enhancing the catalyst's redox capability. Simultaneously, the composite oxide active components can enter the pores of the molecular sieve and interact with elements in the molecular sieve framework; the pores of the molecular sieve block the entry of sulfur dioxide, thereby improving the catalyst's resistance to sulfur dioxide poisoning, ensuring that it still possesses high catalytic activity and nitrogen selectivity even after sulfur dioxide poisoning.

[0015] It should be noted that the SBA series molecular sieves are mesoporous molecular sieves, capable of accommodating complex oxide active components and possessing strong mass transfer capabilities, including the ability to convert NO... x Gases such as NH3 diffuse rapidly to the active sites. The denitrification catalyst prepared in this invention has strong Bronsted and Lewis acidic sites, which can increase the catalyst's adsorption capacity for NH3 and its resistance to sulfur dioxide poisoning.

[0016] In this invention, the particle size D90 of the composite oxide active component is 5-30 nm, for example, it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm or 30 nm, etc.

[0017] In this invention, if the particle size D90 of the composite oxide active component is too small, the crystallinity is poor, which affects the acidity of the active component and thus affects the catalytic performance; if the particle size D90 of the composite oxide active component is too large, it is difficult to enter the pores of the support and cannot form an interaction with the support, thus affecting the catalytic performance.

[0018] As a preferred technical solution of the present invention, the mesoporous SBA molecular sieve carrier includes any one or a combination of at least two of SBA-15 molecular sieve, SBA-16 molecular sieve or SBA-3 molecular sieve, preferably SBA-15 molecular sieve.

[0019] As a preferred embodiment of the present invention, the molar ratio of the dopant element to the Ce element in the active component of the composite oxide is (0.05-0.2):1, for example, it can be 0.05:1, 0.1:1, 0.15:1 or 0.2:1, etc.

[0020] In this invention, if the molar ratio of the dopant element to Ce element is too large, that is, if too much dopant element is used, it will not be able to successfully enter the CeO2 lattice to form a solid solution, and phase separation will occur, thereby affecting the interaction between Ce element and dopant element, thus affecting catalytic performance. If the molar ratio of the dopant element to Ce element is too small, that is, if too little dopant element is used, it will not be able to adjust the acidity and redox ability of CeO2, thus affecting catalytic performance.

[0021] Preferably, the doping element includes any one or a combination of at least two of copper, neodymium, samarium, cobalt, europium, yttrium, dysprosium, ytterbium, lanthanum, iron, zirconium, nickel, or praseodymium.

[0022] Preferably, based on the mass of the denitrification catalyst as 100%, the mass fraction of the composite oxide active component is 5-45%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%, etc., preferably 10-35%.

[0023] In this invention, if the mass fraction of the active component of the composite oxide is too small, the number of active sites will be too few and they will not be able to react with all the gas to be purified; if the mass fraction of the active component of the composite oxide is too large, the active sites will have poor dispersion and will easily agglomerate, thereby affecting the sulfur resistance.

[0024] Preferably, the particle size D90 of the composite oxide active component is 5-15 nm, for example, it can be 5 nm, 10 nm or 15 nm, and preferably 9 nm.

[0025] In a second aspect, the present invention provides a method for preparing a denitrification catalyst as described in the first aspect, the method comprising the following steps:

[0026] The mesoporous SBA molecular sieve and the composite oxide active component are mixed and calcined to obtain the denitrification catalyst.

[0027] The preparation method provided by this invention is relatively simple. This method can adjust the particle size of the active component of the composite oxide, thereby controlling the redox ability and acidity of the catalyst, and further improving the denitrification activity, nitrogen selectivity and sulfur dioxide poisoning resistance of the catalyst.

[0028] The synthesis conditions of this invention are simple and mild, with no byproducts or pollution, and can significantly save synthesis costs and raw material costs.

[0029] As a preferred embodiment of the present invention, the method for preparing the active component of the composite oxide includes:

[0030] (1) Mix the cerium source, surfactant, M source and solvent to obtain a mixture;

[0031] (2) The mixture is mixed with an organic base and subjected to a hydrothermal reaction to obtain the active component of the composite oxide.

[0032] As a preferred technical solution of the present invention, the cerium source in step (1) is a cerium salt, which includes cerium nitrate.

[0033] Preferably, the surfactant in step (1) includes any one or a combination of at least two of polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, or polyethylene glycol.

[0034] It should be noted that the present invention does not limit the type of polyvinylpyrrolidone. For example, it can be PVP-K30, which has a weight-average molecular weight of 45,000.

[0035] Preferably, the M source in step (1) includes an M-containing nitrate.

[0036] Preferably, the concentration of the surfactant in step (1) is 0.005-0.1 g / mL, for example, it can be 0.005 g / mL, 0.01 g / mL, 0.05 g / mL or 0.1 g / mL, etc., and preferably 0.0088 g / mL.

[0037] In this invention, the addition of a surfactant at a concentration of 0.005-0.1 g / mL helps to control the morphology of the active component and form nanospheres.

[0038] Preferably, the organic base in step (2) includes any one or a combination of at least two of triethylamine, diethylamine, diethylenetriamine or ethanolamine.

[0039] Preferably, the concentration of the organic base in step (2) is 0.008-0.012 mL / mL, for example, it can be 0.008 mL / mL, 0.009 mL / mL, 0.010 mL / mL, 0.011 mL / mL or 0.012 mL / mL, etc.

[0040] It should be noted that the concentration of organic base refers to the ratio of the amount of organic base added to the volume of solvent.

[0041] In this invention, the addition of an organic base at a concentration of 0.008-0.012 mL / mL helps the active components to be fully dispersed and form a colloid.

[0042] Preferably, the temperature of the hydrothermal reaction in step (2) is 160-200℃, for example, 160℃, 170℃, 180℃, 190℃ or 200℃, and the time is 18-30h, for example, 18h, 20h, 22h, 24h, 26h, 28h or 30h.

[0043] As a preferred technical solution of the present invention, the method of mixing the mesoporous SBA molecular sieve and the composite oxide active component includes:

[0044] The mesoporous SBA molecular sieve is ground and then dispersed in a solvent to obtain a dispersion. The dispersion is then mixed with the active component of the composite oxide.

[0045] Preferably, after the grinding process, the mesh size of the mesoporous SBA molecular sieve is 30-200 mesh, for example, 30 mesh, 50 mesh, 100 mesh, 150 mesh or 200 mesh, etc., preferably 40-60 mesh.

[0046] Preferably, the concentration of the dispersion is 2-8 g / L, for example, it can be 2 g / L, 4 g / L, 6 g / L or 8 g / L.

[0047] Preferably, the roasting temperature is 400-600℃, for example, 400℃, 450℃, 500℃, 550℃ or 600℃, and the time is 3-10h, for example, 3h, 5h, 7h or 9h.

[0048] Preferably, the heating rate of the calcination is 1-10℃ / min, for example, it can be 1℃, 3℃, 5℃, 7℃ or 9℃, etc.

[0049] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0050] (I) A mixture is prepared by mixing cerium salt, surfactant, M-containing nitrate and solvent to obtain a mixture;

[0051] The concentration of the surfactant is 0.005-0.1 g / mL;

[0052] (II) Mix the mixture with the organic base and stir for 8-12 min, and then carry out a hydrothermal reaction at 160-200℃ for 18-30 h to obtain the active component of the composite oxide;

[0053] The concentration of the organic base is 0.008-0.012 mL / mL;

[0054] (III) Grind the mesoporous SBA molecular sieve to a mesh size of 30-200 mesh, and then ultrasonically disperse it in a solvent for 10-60 min to obtain a dispersion with a concentration of 2-8 g / L.

[0055] The dispersion and the active component of the composite oxide are mixed and stirred, and then evaporated to dryness at 60-90℃. The mixture is then calcined at 400-600℃ for 3-10 hours at a heating rate of 1-10℃ / min to obtain the denitrification catalyst.

[0056] Thirdly, the present invention provides an application of the denitrification catalyst as described in the first aspect, characterized in that the denitrification catalyst is used for the selective catalytic reduction of nitrogen oxides by ammonia;

[0057] Preferably, the operating temperature of the denitrification catalyst is 150-550℃, for example, it can be 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ or 550℃, etc., preferably 200-400℃.

[0058] Fourthly, the present invention provides a denitrification reactor, the denitrification reactor comprising the denitrification reactor described in the first aspect, the denitrification reactor being used for a mobile source gas denitrification device and / or a stationary source gas denitrification device.

[0059] Preferably, the mobile source gas denitrification device includes any one or a combination of at least two of a diesel engine, a gas turbine, or an aircraft engine.

[0060] Preferably, the stationary source gas denitrification device includes an industrial kiln and / or a calcining kiln.

[0061] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] (1) The denitrification catalyst of the present invention has high surface acidity and redox ability, CeMO x The interaction with the support enhances the catalyst's resistance to sulfur dioxide poisoning, thereby ensuring that it maintains high catalytic activity and nitrogen selectivity within the operating temperature range of 250-400℃ after sulfur dioxide poisoning.

[0064] (2) The preparation method provided by the present invention has simple and mild synthesis conditions, no by-products and pollution, and can significantly save synthesis cost and raw material cost. Attached Figure Description

[0065] Figure 1 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Example 1 of this invention.

[0066] Figure 2 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Comparative Example 4 of this invention.

[0067] Figure 3 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Comparative Example 5 of this invention.

[0068] Figure 4 This is a TEM image of the denitrification catalyst prepared in Comparative Example 6 of this invention.

[0069] Figure 5 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Comparative Example 6 of this invention.

[0070] Figure 6 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Comparative Example 9 of this invention.

[0071] Figure 7 The figures show the nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate diagram in the presence of sulfur dioxide for the denitrification catalyst prepared in Comparative Example 10 of this invention. Detailed Implementation

[0072] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0073] Example 1

[0074] This embodiment provides a denitrification catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0075] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeCuO. x Where x is the number of O atoms required to satisfy valence equilibrium;

[0076] The particle size D90 of the composite oxide active component is 9 nm; the molar ratio of the doping elements Cu and Ce in the composite oxide active component is 0.11:1; and the mass fraction of the composite oxide active component is 35% based on 100% of the mass of the denitrification catalyst.

[0077] This embodiment also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0078] (1) Dissolve 0.0391g of cerium nitrate hexahydrate, 0.8g of surfactant and 0.00188g of copper nitrate in 40mL of ethanol to obtain a mixture;

[0079] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0080] (2) The mixture and 0.352 mL of triethylamine were mixed and stirred for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0081] The concentration of triethylamine was 0.0088 mL / mL.

[0082] (3) Grind 0.032g of SBA-15 molecular sieve to a mesh size of 50 mesh, and then ultrasonically disperse it in 10mL of deionized water for 30min to obtain a dispersion with a concentration of 3.2g / L.

[0083] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 5 °C / min for 4 h to obtain the denitrification catalyst.

[0084] Figure 1 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide of the denitrification catalyst prepared in this embodiment are shown. As can be seen from the graph, the catalyst prepared in this embodiment purified more than 90% of the nitrogen oxides at temperatures above 300°C, while maintaining a nitrogen selectivity of over 90%. After introducing sulfur dioxide into the reaction atmosphere, the nitrogen oxide conversion rate of this catalyst is not less than 95%.

[0085] Example 2

[0086] This embodiment provides a denitrification catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0087] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeCuO. x Where x is the number of O atoms required to satisfy valence equilibrium;

[0088] The particle size D90 of the composite oxide active component is 9 nm; the molar ratio of the doping elements Cu and Ce in the composite oxide active component is 0.2:1; and the mass fraction of the composite oxide active component is 35% based on 100% of the mass of the denitrification catalyst.

[0089] This embodiment also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0090] (1) Dissolve 0.0434 g of cerium nitrate hexahydrate, 0.8 g of surfactant and 0.00375 g of copper nitrate in 40 mL of ethanol to obtain a mixture;

[0091] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0092] (2) The mixture and 0.352 mL of triethylamine were mixed and stirred for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0093] The concentration of triethylamine was 0.0088 mL / mL.

[0094] (3) Grind 0.032g of SBA-15 molecular sieve to a mesh size of 50 mesh, and then ultrasonically disperse it in 8mL of deionized water for 30min to obtain a dispersion with a concentration of 4g / L.

[0095] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 8 °C / min for 4 h for calcination to obtain the denitrification catalyst.

[0096] Example 3

[0097] This embodiment provides a denitrification catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0098] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeFeO. x Where x is the number of O atoms required to satisfy valence equilibrium;

[0099] The particle size D90 of the composite oxide active component is 9 nm; the molar ratio of the doping elements Fe and Ce in the composite oxide active component is 0.2:1; and the mass fraction of the composite oxide active component is 35% based on 100% of the mass of the denitrification catalyst.

[0100] This embodiment also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0101] (1) Dissolve 0.0391g of cerium nitrate hexahydrate, 0.8g of surfactant and 0.00338g of copper nitrate in 40mL of ethanol to obtain a mixture;

[0102] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0103] (2) The mixture and 0.352 mL of triethylamine were mixed and stirred for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0104] The concentration of triethylamine was 0.0088 mL / mL.

[0105] (3) Grind 0.032g of SBA-15 molecular sieve to a mesh size of 50 mesh, then ultrasonically disperse it in 4mL of deionized water for 30min to obtain a dispersion with a concentration of 8g / L.

[0106] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 10 °C / min for 4 h to obtain the denitrification catalyst.

[0107] Example 4

[0108] This embodiment provides a denitrification catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0109] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeCoO. x Where x is the number of O atoms required to satisfy valence equilibrium;

[0110] The particle size D90 of the composite oxide active component is 5 nm; the molar ratio of the doping elements Co and Ce in the composite oxide active component is 0.05:1; and the mass fraction of the composite oxide active component is 20% based on 100% of the mass of the denitrification catalyst.

[0111] This embodiment also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0112] (I) Dissolve 0.0391g of cerium nitrate hexahydrate, 2g of surfactant and 0.000582g of cobalt nitrate in 40mL of ethanol to obtain a mixture;

[0113] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.05 g / mL.

[0114] (II) The mixture is mixed with 0.352 mL of triethylamine and stirred for 8 min, and then subjected to a hydrothermal reaction at 160 °C for 30 h to obtain the active component of the composite oxide;

[0115] The concentration of triethylamine was 0.0088 mL / mL.

[0116] (III) Grind 0.1g of SBA-15 molecular sieve to a mesh size of 40, then ultrasonically disperse it in 50mL of deionized water for 10min to obtain a dispersion with a concentration of 2g / L.

[0117] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 60 °C, and then placed in a muffle furnace and heated to 400 °C at a heating rate of 5 °C / min for 10 h to obtain the denitrification catalyst.

[0118] Example 5

[0119] This embodiment provides a denitrification catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0120] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeNiO. x Where x is the number of O atoms required to satisfy valence equilibrium;

[0121] The particle size D90 of the composite oxide active component is 15 nm; the molar ratio of the doping elements Ni and Ce in the composite oxide active component is 0.14:1; and the mass fraction of the composite oxide active component is 10% based on the mass of the denitrification catalyst being 100%.

[0122] This embodiment also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0123] (I) Dissolve 0.0391g of cerium nitrate hexahydrate, 4g of surfactant and 0.0023g of nickel nitrate in 40mL of ethanol to obtain a mixture;

[0124] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45,000), and the concentration of the surfactant was 0.1 g / mL.

[0125] (II) The mixture is mixed with 0.352 mL of triethylamine and stirred for 12 min, and then subjected to a hydrothermal reaction at 200 °C for 18 h to obtain the active component of the composite oxide;

[0126] The concentration of triethylamine was 0.0088 mL / mL.

[0127] (III) Grind 0.4g of SBA-15 molecular sieve to a mesh size of 60 mesh, then ultrasonically disperse it in 50mL of deionized water for 60min to obtain a dispersion with a concentration of 8g / L.

[0128] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 90 °C. The mixture was then placed in a muffle furnace and heated to 600 °C at a heating rate of 10 °C / min for 3 h to obtain the denitrification catalyst.

[0129] Example 6

[0130] The difference between this embodiment and embodiment 1 is that the amount of copper nitrate added in step (1) is adjusted so that the molar ratio of the dopant elements Cu and Ce is 0.02:1.

[0131] The remaining preparation methods and parameters are consistent with those in Example 1.

[0132] Example 7

[0133] The difference between this embodiment and embodiment 1 is that the amount of copper nitrate added in step (1) is adjusted so that the molar ratio of the dopant elements Cu and Ce is 0.3:1.

[0134] The remaining preparation methods and parameters are consistent with those in Example 1.

[0135] Example 8

[0136] The difference between this embodiment and embodiment 1 is that the amount of composite oxide active component added in step (3) is adjusted so that the mass fraction of composite oxide active component in the denitrification catalyst is 2%.

[0137] The remaining preparation methods and parameters are consistent with those in Example 1.

[0138] Example 9

[0139] The difference between this embodiment and embodiment 1 is that the amount of composite oxide active component added in step (3) is adjusted so that the mass fraction of composite oxide active component in the denitrification catalyst is 50%.

[0140] The remaining preparation methods and parameters are consistent with those in Example 1.

[0141] Example 10

[0142] The difference between this embodiment and Embodiment 1 is that no surfactant is added in step (1).

[0143] The remaining preparation methods and parameters are consistent with those in Example 1.

[0144] Example 11

[0145] The difference between this embodiment and embodiment 1 is that triethylamine is not added in step (2).

[0146] The remaining preparation methods and parameters are consistent with those in Example 1.

[0147] Comparative Example 1

[0148] The difference between this comparative example and Example 1 is that copper nitrate is not added in step (1).

[0149] The remaining preparation methods and parameters are consistent with those in Example 1.

[0150] Comparative Example 2

[0151] The difference between this comparative example and Example 1 is that the amount of surfactant added was adjusted so that the particle size D90 of the composite oxide active component was 3 nm.

[0152] The remaining preparation methods and parameters are consistent with those in Example 1.

[0153] Comparative Example 3

[0154] The difference between this comparative example and Example 1 is that the amount of surfactant added was adjusted so that the particle size D90 of the composite oxide active component was 35 nm.

[0155] The remaining preparation methods and parameters are consistent with those in Example 1.

[0156] Comparative Example 4

[0157] This comparative example provides a method for preparing a CeO2 catalyst, the method comprising the following steps:

[0158] 0.0434 g of cerium nitrate hexahydrate and 0.8 g of polyvinylpyrrolidone (PVP-K30, weight average molecular weight 45000) were added to 40 mL of ethanol, and then 0.352 mL of triethylamine was added. The mixture was stirred for 10 min and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain a cerium-based active component with a particle size of 9 nm.

[0159] The cerium-based active component was stirred and evaporated to dryness at 85°C, and then placed in a muffle furnace at a heating rate of 5°C / min and calcined at 500°C for 4 hours to obtain the CeO2 catalyst.

[0160] Figure 2 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide of the denitrification catalyst prepared in this comparative example are shown. As can be seen from the graph, the highest nitrogen oxide purification rate of this catalyst does not exceed 60%, and the nitrogen selectivity is always not lower than 95%. However, after SO2 is introduced, the performance of the catalyst drops significantly, and its nitrogen oxide purification rate drops from 100% to 70%, and cannot be recovered after SO2 is disconnected.

[0161] Comparative Example 5

[0162] This comparative example provides a method for preparing a vanadium-tungsten-titanium (V2O5-WO3 / TiO2) catalyst, the preparation method comprising the following steps:

[0163] 0.9 g of oxalic acid dihydrate was dissolved in 50 mL of deionized water, and then 0.0128 g of ammonium metavanadate and 0.2027 g of ammonium paratungstate were added. After all the solids were dissolved, 1.8 g of TiO2 was added. The resulting mixture was stirred and evaporated to dryness at 90 °C, and then placed in a muffle furnace at a heating rate of 5 °C / min and calcined at 500 °C for 4 hours to obtain a vanadium-tungsten-titanium (V2O5-WO3 / TiO2) catalyst.

[0164] Figure 3 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide are shown for the denitrification catalyst prepared in this comparative example. As can be seen from the graph, the nitrogen oxide purification rate of the vanadium-tungsten-titanium catalyst at 250-400℃ does not exceed 80%, and its nitrogen selectivity is only 95% at its highest, indicating a large number of side reactions. After introducing SO2, the nitrogen oxide conversion rate of this catalyst remains unchanged at 70%.

[0165] Comparative Example 6

[0166] This comparative example provides a denitration catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0167] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeO2;

[0168] The particle size D90 of the composite oxide active component is 7 nm; the mass fraction of the composite oxide active component is 10% based on the mass of the denitrification catalyst being 100%.

[0169] This comparative example also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0170] (1) Dissolve 0.0434 g of cerium nitrate hexahydrate and 0.8 g of surfactant in 40 mL of ethanol to obtain a mixture;

[0171] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0172] (2) The mixture was stirred with 0.8 mL of triethylamine for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0173] The concentration of triethylamine was 0.02 mL / mL.

[0174] (3) Grind 0.155g of SBA-15 molecular sieve to a mesh size of 50 mesh, and then ultrasonically disperse it in 50mL of deionized water for 30min to obtain a dispersion with a concentration of 3.1g / L.

[0175] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 10 °C / min for 4 h to obtain the denitrification catalyst.

[0176] Figure 4 The TEM image of the denitrification catalyst prepared in this comparative example is shown. As can be seen from the figure, the morphology of the active component is nanospheres. A large number of nanospheres have entered the pores of the catalyst, but some nanospheres are also distributed on the surface of the catalyst.

[0177] Figure 5 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide are shown for the denitrification catalyst prepared in this comparative example. As can be seen from the graph, the catalyst converted more than 80% of the nitrogen oxides within the temperature range of 260-360℃, while maintaining a nitrogen selectivity of no less than 95%. After introducing SO2, the catalyst performance remained consistently above 88%.

[0178] Comparative Example 7

[0179] This comparative example provides a denitration catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0180] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeO2;

[0181] The particle size D90 of the composite oxide active component is 7 nm; the mass fraction of the composite oxide active component is 35% based on the mass of the denitrification catalyst being 100%.

[0182] This comparative example also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0183] (1) Dissolve 0.0434 g of cerium nitrate hexahydrate and 0.8 g of surfactant in 40 mL of ethanol to obtain a mixture;

[0184] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0185] (2) The mixture was stirred with 0.8 mL of triethylamine for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0186] The concentration of triethylamine was 0.02 mL / mL.

[0187] (3) Grind 0.032g of SBA-15 molecular sieve to a mesh size of 50 mesh, and then ultrasonically disperse it in 50mL of deionized water for 30min to obtain a dispersion with a concentration of 0.64g / L.

[0188] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 10 °C / min for 4 h to obtain the denitrification catalyst.

[0189] Comparative Example 8

[0190] This comparative example provides a denitration catalyst, which includes a support and a composite oxide active component supported on the surface of the support;

[0191] The support is SBA-15 molecular sieve, and the chemical formula of the active component of the composite oxide is CeO2;

[0192] The particle size D90 of the composite oxide active component is 7 nm; the mass fraction of the composite oxide active component is 45% based on the mass of the denitrification catalyst being 100%.

[0193] This comparative example also provides a method for preparing the above-mentioned denitrification catalyst, the method comprising the following steps:

[0194] (1) Dissolve 0.0434 g of cerium nitrate hexahydrate and 0.8 g of surfactant in 40 mL of ethanol to obtain a mixture;

[0195] The surfactant used was polyvinylpyrrolidone (PVP-K30, weight-average molecular weight 45000), and the concentration of the surfactant was 0.02 g / mL.

[0196] (2) The mixture was stirred with 0.8 mL of triethylamine for 10 min, and then subjected to a hydrothermal reaction at 180 °C for 24 h to obtain the active component of the composite oxide;

[0197] The concentration of triethylamine was 0.02 mL / mL.

[0198] (3) Grind 0.021g of SBA-15 molecular sieve to a mesh size of 50 mesh, and then ultrasonically disperse it in 50mL of deionized water for 30min to obtain a dispersion with a concentration of 0.42 / L.

[0199] The dispersion and the active component of the composite oxide were mixed and stirred for 30 min, then stirred and evaporated to dryness at 85 °C, and then placed in a muffle furnace and heated to 500 °C at a heating rate of 10 °C / min for 4 h to obtain the denitrification catalyst.

[0200] Comparative Example 9

[0201] The difference between this comparative example and comparative example 7 is that the amount of triethylamine added in step (2) is 0.352 mL, so that the particle size D90 of the active component of the composite oxide is 9 nm.

[0202] The remaining preparation methods and parameters are consistent with those of Comparative Example 7.

[0203] Figure 6 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide of the denitrification catalyst prepared in this comparative example are shown. As can be seen from the graph, the catalyst purified more than 80% of nitrogen oxides within the temperature range of 270-380℃, while the nitrogen selectivity remained above 95%. After introducing SO2, the catalyst performance did not show a significant decrease within 20 hours, consistently remaining above 95%.

[0204] Comparative Example 10

[0205] The difference between this comparative example and comparative example 7 is that the amount of triethylamine added in step (2) is adjusted to 0.2 mL and the amount of surfactant added is 0.2 g, so that the particle size D90 of the active component of the composite oxide is 25 nm.

[0206] The remaining preparation methods and parameters are consistent with those of Comparative Example 7.

[0207] Figure 7 The nitrogen oxide purification rate curve, nitrogen selectivity curve, and nitrogen oxide purification rate graph in the presence of sulfur dioxide of the denitrification catalyst prepared in this comparative example are shown. As can be seen from the graph, the highest nitrogen oxide purification rate of the catalyst does not exceed 60%. Furthermore, the nitrogen selectivity at high temperature is only 83%. After introducing SO2, the nitrogen oxide purification rate of the catalyst decreases from 75% to 60%.

[0208] Comparative Example 11

[0209] The difference between this comparative example and comparative example 7 is that the amount of triethylamine added in step (2) is adjusted to 0.2 mL and the amount of surfactant added is 1.2 g, so that the particle size D90 of the active component of the composite oxide is 6 nm.

[0210] The remaining preparation methods and parameters are consistent with those of Comparative Example 7.

[0211] Comparative Example 12

[0212] The difference between this comparative example and comparative example 7 is that the amount of triethylamine added in step (2) is adjusted to 0.2 mL and the amount of surfactant added is 2 g, so that the particle size D90 of the active component of the composite oxide is 5 nm.

[0213] The remaining preparation methods and parameters are consistent with those of Comparative Example 7.

[0214] Comparative Example 13

[0215] The difference between this comparative example and comparative example 9 is that the SBA-15 molecular sieve is replaced with SBA-3.

[0216] The remaining preparation methods and parameters are consistent with those of Comparative Example 9.

[0217] Comparative Example 14

[0218] The difference between this comparative example and comparative example 9 is that the SBA-15 molecular sieve is replaced with TiO2.

[0219] The remaining preparation methods and parameters are consistent with those of Comparative Example 9.

[0220] Performance testing

[0221] The catalysts prepared using the above examples and comparative examples were used to conduct denitrification activity experiments on simulated flue gas.

[0222] The simulated flue gas contained 500 ppm NH3, 500 ppm NO, and 5% O2, with nitrogen as the balance gas. Subsequently, the denitrification activity of the catalyst was tested using simulated flue gas containing sulfur dioxide. The simulated flue gas contained 500 ppm NH3, 500 ppm NO, 100 ppm SO2, and 5% O2, with nitrogen as the balance gas.

[0223] The test results are shown in Table 1.

[0224] Table 1

[0225]

[0226]

[0227] analyze:

[0228] As shown in the table above, the denitrification catalyst of this invention has high surface acidity and redox ability, and CeMO... xThe interaction with the support enhances the catalyst's resistance to sulfur dioxide poisoning, thereby ensuring that it maintains high catalytic activity and nitrogen selectivity within the operating temperature range of 250-400℃ after sulfur dioxide poisoning.

[0229] The data from Examples 1 and 6-7 show that if the molar ratio of dopant elements Cu and Ce is too small, there will be too few atoms that interact with Ce and Cu, resulting in limited improvement in catalyst performance. If the molar ratio of dopant elements Cu and Ce is too large, too much Cu will cause phase separation, and the redox ability of a large amount of CuO at high temperature will be too strong, resulting in excessive ammonia oxidation at high temperature, and a large amount of ammonia will be oxidized into nitrogen oxides.

[0230] The data results from Examples 1 and 8-9 show that if the mass fraction of the composite oxide active component in the denitration catalyst is too small, there will be too few active sites, resulting in poor catalyst performance; if the mass fraction of the composite oxide active component in the denitration catalyst is too large, the active component will have poor dispersion and nanoparticles will agglomerate, resulting in poor utilization of active sites.

[0231] The data results from Examples 1 and 10-11 show that if no surfactant is added in step (1), the active component becomes uneven particles, resulting in uneven dispersion of the active component and poor utilization of active sites. If no triethylamine is added in step (2), the active component cannot be dispersed in the solvent and becomes a colloid, resulting in agglomeration. In the subsequent synthesis process, it cannot be fully dispersed on the carrier, thus resulting in poor utilization of active sites.

[0232] The data from Example 1 and Comparative Example 1 show that if the active component of the composite oxide is not doped with elements, the active component of the catalyst contains only CeO2, and its catalytic performance is poor in the low-temperature range.

[0233] The data from Example 1 and Comparative Examples 2-3 show that if the particle size D90 of the composite oxide active component is too small, the interaction between the active component and the support is not strong enough, which makes it easy to be sulfided and reduces the catalytic performance. If the particle size D90 of the composite oxide active component is too large, the active component is completely dispersed on the surface and does not easily enter the pores of the catalyst, which also makes the active component easy to be sulfided.

[0234] The data from Example 1 and Comparative Examples 4-5 show that the CeO2 catalyst has a wide temperature range, high nitrogen selectivity, and excellent sulfur resistance, while the vanadium-tungsten-titanium (V2O5-WO3 / TiO2) catalyst has a narrow temperature range, poor nitrogen selectivity, and relatively good sulfur resistance.

[0235] The data from Comparative Examples 6-8 show that when the particle size of the active component is the same and the loading of the active component is 35%, the catalyst has the best nitrogen oxide purification rate and sulfur dioxide resistance.

[0236] The data from Comparative Examples 7 and 9-12 show that when the loading of the active component is 35%, among the supported catalysts made of active components with particle sizes of 5 nm, 6 nm, 7 nm, 9 nm and 25 nm, the catalyst with a particle size of 9 nm has the best nitrogen oxide purification rate and sulfur dioxide resistance.

[0237] The data from Examples 1 and 3 show that the cerium-based denitration catalyst doped with copper has a stronger denitration capacity than other catalysts. Copper plays an important role in resisting sulfur dioxide poisoning and enhancing low-temperature performance. When copper is replaced with other elements such as iron, the redox capacity of the catalyst decreases, and the resistance to sulfur dioxide poisoning also decreases.

[0238] The data from Comparative Examples 9 and 13 show that the catalyst using SBA-15 as the support has a stronger denitrification capacity compared to the catalyst using SBA-3 as the support.

[0239] The data from Comparative Examples 9 and 14 show that the mesoporous SBA molecular sieve support has a strong interlayer mass transfer capability, and can transfer NO... x Gases such as NH3 diffuse rapidly to the active sites.

[0240] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A denitrification catalyst, characterized in that, The denitrification catalyst includes a support and a composite oxide active component supported on the surface of the support; The support comprises a mesoporous SBA molecular sieve, and the chemical formula of the active component of the composite oxide is CeMO. x Where M is the doping element and x is the number of O atoms required to satisfy valence balance; The mesoporous SBA molecular sieve support is SBA-15 molecular sieve. The particle size D90 of the active component of the composite oxide is 9 nm; In the active component of the composite oxide, the molar ratio of the dopant element to the Ce element is 0.11:1; The doping element is copper; Based on the mass of the denitrification catalyst being 100%, the mass fraction of the active component of the composite oxide is 25%-35%.

2. A method for preparing the denitrification catalyst as described in claim 1, characterized in that, The preparation method includes the following steps: The mesoporous SBA molecular sieve and the composite oxide active component are mixed and calcined to obtain the denitrification catalyst.

3. The preparation method according to claim 2, characterized in that, The preparation method of the active component of the composite oxide includes: (1) Mix the cerium source, surfactant, M source and solvent to obtain a mixture; (2) The mixture and organic base are mixed and subjected to hydrothermal reaction to obtain the active component of the composite oxide.

4. The preparation method according to claim 3, characterized in that, The cerium source in step (1) is a cerium salt, which includes cerium nitrate.

5. The preparation method according to claim 3, characterized in that, The surfactant in step (1) includes any one or a combination of at least two of polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, or polyethylene glycol.

6. The preparation method according to claim 3, characterized in that, The M source in step (1) includes nitrates containing M.

7. The preparation method according to claim 3, characterized in that, The concentration of the surfactant in step (1) is 0.005-0.1 g / mL.

8. The preparation method according to claim 3, characterized in that, The organic base in step (2) includes any one or a combination of at least two of triethylamine, diethylamine, diethylenetriamine or ethanolamine.

9. The preparation method according to claim 3, characterized in that, The concentration of the organic base in step (2) is 0.008-0.012 mL / mL.

10. The preparation method according to claim 3, characterized in that, The hydrothermal reaction in step (2) is carried out at a temperature of 160-200℃ for 18-30 hours.

11. The preparation method according to claim 3, characterized in that, The method of mixing the mesoporous SBA molecular sieve and the composite oxide active component includes: The mesoporous SBA molecular sieve is ground and then dispersed in a solvent to obtain a dispersion. The dispersion is then mixed with the active component of the composite oxide.

12. The preparation method according to claim 11, characterized in that, After the grinding process, the mesh size of the mesoporous SBA molecular sieve is 30-200 mesh.

13. The preparation method according to claim 12, characterized in that, After the grinding process, the mesh size of the mesoporous SBA molecular sieve is 40-60 mesh.

14. The preparation method according to claim 11, characterized in that, The concentration of the dispersion is 2-8 g / L.

15. The preparation method according to claim 2, characterized in that, The roasting temperature is 400-600℃ and the time is 3-10h.

16. The preparation method according to claim 2, characterized in that, The heating rate for roasting is 1-10℃ / min.

17. The preparation method according to claim 2, characterized in that, The preparation method includes the following steps: (I) A mixture is prepared by mixing cerium salt, surfactant, nitrate containing M, and solvent to obtain a mixture; The concentration of the surfactant is 0.005-0.1 g / mL; (II) Mix the mixture with the organic base and stir for 8-12 min, and then carry out a hydrothermal reaction at 160-200℃ for 18-30 h to obtain the active component of the composite oxide; The concentration of the organic base is 0.008-0.012 mL / mL; (III) Grind the mesoporous SBA molecular sieve to a mesh size of 30-200 mesh, and then ultrasonically disperse it in a solvent for 10-60 min to obtain a dispersion with a concentration of 2-8 g / L; The dispersion and the active component of the composite oxide are mixed and stirred, and then evaporated to dryness at 60-90℃. The mixture is then calcined at 400-600℃ for 3-10 hours at a heating rate of 1-10℃ / min to obtain the denitrification catalyst.

18. The application of a denitrification catalyst as described in claim 1, characterized in that, The denitrification catalyst is used for the selective catalytic reduction of nitrogen oxides by ammonia.

19. The application according to claim 18, characterized in that, The denitrification catalyst operates at a temperature of 150-550℃.

20. The application according to claim 19, characterized in that, The denitrification catalyst operates at a temperature of 200-400℃.

21. A denitrification reactor, characterized in that, The denitrification reactor includes the denitrification catalyst as described in claim 1, and the denitrification reactor is used in mobile source gas denitrification devices and / or stationary source gas denitrification devices.

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